Interpretive Summary: Phosphorus (P) accumulates in soils that are over fertilized with broiler litter, a mixture of manure, wasted feed, and bedding materials. Studies suggest overseeding bermudagrass with annual ryegrass and removing forage biomass from the production site may help to remediate soils with excess P (levels in excess of crop needs). Field studies were conducted to determine if ryegrass-bermudagrass removes more soil P than a bermudagrass winter fallow system after litter applications cease. During the build-up phase, bermudagrass was fertilized with five rates of litter in Spring 1999, 2000, and 2001. During the remediation phase, half the plot remained in bermudagrass and the other half was overseeded with annual ryegrass in Fall 2001,2002 and 2003. Nitrogen fertilizer was applied as recommended for bermudagrass production. Forage biomass and P uptake by both forage systems increased as litter rate increased. In the 4 ton/acre treatment, harvesting ryegrass in addition to bermudagrass increased P uptake by about 30%, and after two years had decreased soil test P from about 116 to 62 parts per million. Because repeated hay harvests decreased water-extractable P concentration in soil, both forage systems have potential to reduce off-site P movement. Results impact the forage and broiler industries in the Midsouth USA by providing information on the long-term economic value and sustainability of fertilizing bermudagrass hay fields with broiler litter.

Technical Abstract:
Phosphorus accumulation occurs in soils that are over fertilized with manure. Previous studies indicate overseeding bermudagrass with annual ryegrass can remove more nutrients from manure-treated soils than bermudagrass winter-fallow system. This study determined if harvesting ryegrass hay in addition to bermudagrass would reduce surplus soil P faster than bermudagrass alone. During the build-up phase, bermudagrass was fertilized with five rates of litter in Spring 1999, 2000, and 2001. During the remediation phase, half the plot remained in bermudagrass and the other half was overseeded with ryegrass in Fall 2001, 2002 and 2003. Fertilizer N was applied as recommended for bermudagrass. Soil analysis, 0-15 cm depth, from five sampling dates found relatively large decreases in Mehlich 3 P (M3P) at 36 Mg/ha litter due to increased biomass yield. Analysis of M3P within a sampling date found no significant effect of forage system or its interaction with litter rate. In the 9 Mg/ha litter treatment, harvesting ryegrass in addition to bermudagrass increased P uptake by about 30% (range = 10-55% across years). Based on linear interpolation of means, two years of forage P removal would be needed to decrease M3P to an acceptable level, i.e., below 70 mg/kg. Results confirm the effectiveness of annual ryegrass to increase total P uptake, and demonstrate a major benefit from harvesting two common forage crops on remediation of excess soil P in a Ruston soil.